1. Field of the Invention
The present invention relates to an improved curing composition comprising a specific water soluble high-molecular compound having a cationic group in the principal molecular chain thereof and another specific water soluble high-molecular compound having a crosslinking property, which is capable of providing a condensed and crosslinked structure or a polymerized and crosslinked structure upon the application of thermal energy or the irradiation of ultraviolet rays and which enables to form a desirable ink-receiving layer which excels in waterfastness and ink receiving property. The present invention includes a printing medium formed of said curing composition and a process for producing a print product with the use of said curing composition.
2. Related Background Art
In recent years, an ink jet recording system has made rapid progress in the digital recording system field, and it has been widely used as an outputting terminal printer for personal computers, particularly used in offices. This situation is based on an outcome that a recording apparatus having a desirable printability for a recording medium having a hygroscopic property to water-based ink has been developed.
As such ink jet recording system, there have been proposed various ink jet recording apparatus. These ink jet recording apparatus are mostly of the so-called bubble jet system in which thermal energy is utilized for discharging ink. In the bubble jet recording apparatus, there is usually used water-based ink for performing printing for a printing medium. Therefore, particularly in the case where the bubble jet recording apparatus is used as a printing apparatus for producing a volume of print products, due care must be used with printing mediums to be dedicated for printing because they are often poor in absorption of said water-based ink. As such printing medium dedicated for printing in this, there can be mentioned, for examples, metal members, plastic members, rubber members, ceramics, fabrics, leathers, glass products, and food products. In the case where the printing medium does not have a sufficient property of absorbing the water-based ink, the printing medium is necessary to be designed such that it has an ink-absorptive layer (that is, an ink-receiving layer).
By the way, there are known coating compositions for OHP films which have been designed to be suitable for the printing by the ink jet printing apparatus. However, these coating compositions are not suitable for use in the case of industrially printing any of the above mentioned materials poor in absorption of the water-based ink by the ink jet printing apparatus, because any of the coating compositions is difficult to form a film as an ink-receiving layer which is insufficient in adhesion, coating suitability, and durability against a substrate comprising any of the above mentioned materials dedicated for printing by the ink jet printing apparatus.
Now, as for the ink-receiving layer formed on such material poor in absorption of the water-based ink so that printing by the ink jet printing apparatus can be desirably conducted, the ink-receiving layer is necessary to be formed of a material which satisfies the following conditions:
(i) the material enables to form a desirable film as an ink-receiving layer within a short period of time, PA1 (ii) the material enables to form a desirable film as an ink-receiving layer which has a sufficient adhesion against a substrate, PA1 (iii) the material enables to form a desirable film as an ink-receiving layer which allows ink to be shortly fixed thereon, PA1 (iv) the material enables to form a desirable film as an ink-receiving layer which allows coloring components (dyes and pigments) of ink to be strongly fixed thereon, PA1 (v) the material enables to form a desirable film as an ink-receiving layer which allows the formation of a clear image at a high resolution thereon, and PA1 (vi) the material enables to form a desirable film as an ink-receiving layer which excels in fastness properties. PA1 (C) water soluble acrylic polymers obtained by cationizing an acrylic ester series copolymer having a side chain with a terminal hydroxyl group, and PA1 (D) water soluble cationized polyvinyl alcohols having a molecular chain containing 2 to 15 mole % of cationic group which are obtained from a polyvinyl alcohol of 80 mole % or more in saponification value by cationinzing the hydroxyl group of the polyvinyl alcohol. PA1 (E) acrylamide series high-molecular compounds having an acrylamide-bearing alkylol group as a side chain, and PA1 (F) acrylic ester series high-molecular compounds having a hydrolyzable trialkylsilyl group. PA1 monomers represented by the following general formula. PA1 CH.sub.2 .dbd.C(CH.sub.3)--COO--(CH.sub.2 CH.sub.2 O).sub.n --H, with n being 1.9; PA1 CH.sub.2 .dbd.C(CH.sub.3)--COO--(CH.sub.2 CH.sub.2 O).sub.n --H, with n being 4.4; and PA1 CH.sub.2 .dbd.C(CH.sub.3)--COO--(CH.sub.2 CH.sub.2 O).sub.n --H, with n being 7.7. PA1 monomers represented by the following general formula. PA1 methoxytriethylene glycol acrylate NK ESTER AM-30G (trademark name, R=H, m=3, p=1); PA1 methoxypolyethylene glycol #400 acrylate NK ESTER AM-90G (trademark name, R=H, m=about 10, p=1); PA1 methoxydiethylene glycol methacrylate NK ESTER M-20G (trademark name, R=CH.sub.3, m=2, p=1); PA1 methoxytetraethylene glycol methacrylate NK ESTER M-40G (trademark name, R=CH.sub.3, m=4, p=1); PA1 methoxypolyethylene glycol #400 methacrylate NK ESTER M-90G (trademark name, R=CH.sub.3, m=about 10, p=1); PA1 methoxypolythylene glycol #100 methacrylate NK ESTER M-230G (trademark name, R=CH.sub.3, m=about 24, p=1); and PA1 methoxydiethylene glycol acrylate NK ESTER AB-20G (trademark name, R=H, m=2, p=4).
As the material by which a desirable film as an ink-receiving layer which satisfies these requirements is formed, it is considered effective to use a crosslinkable high-molecular compound and an activation energy-curable hydrophilic oligomer.
As for the recording medium, particularly for instance, the OHP film, dedicated for the printing by the ink jet printing apparatus, there have been made various proposals in view of attaining a desirable ink absorption therefor and attaining a desirable waterfastness for a print product. Such proposals are disclosed, for example, in Japanese Unexamined Patent Publications Nos. 94379/1987 (corresponding to U.S. Pat. No. 4,741,969), 94380/1987, 221591/1987, 242578/1987, 229685/1989, and 286886/1989.
Particularly, U.S. Pat. No. 4,741,969 discloses an aqueous ink recording sheet having an ink-receiving layer formed by photo-curing an anionic synthetic resin having a photopolymerizable double bond. However, in the formation of the ink-receiving layer in this document, it is essential to use polymer reaction of bonding an independent reactive monomer to a side chain of a given high-molecular compound. Because of this, there is a problem in that the production cost of the aqueous ink recording sheet unavoidably becomes high. In addition, there is also another problem in that it is quite difficult to stably synthesize a desired synthetic resin at a high reproducibility.
Japanese Unexamined Patent Publication No. 94380/1987 discloses an aqueous ink recording sheet having an ink-receiving layer formed by photo-curing a cationic synthetic resin having a photopolymerizable double bond. However, in the formation of the ink-receiving layer in this document, it is essential to use polymer reaction of bonding an independent reactive monomer to a side chain of a given high-molecular compound. Because of this, there is a problem in that the production cost of the aqueous ink recording sheet unavoidably becomes high. In addition, there is also another problem in that it is quite difficult to stably synthesize a desired synthetic resin at a high reproducibility.
Japanese Unexamined Patent Publication No. 221591/1987 discloses an aqueous ink recording sheet having a two-layered ink-receiving layer comprising a coating layer comprised of an anionic acrylic copolymer cured with the irradiation of ultraviolet rays as a principal component and a coating layer comprised of a cationic acrylic copolymer cured with the irradiation of ultraviolet rays as a principal component. The two-layered ink-receiving layer described in this document is featured in utilizing an ion complex present in the interfacial region between one layer comprised of an electrolytic high-molecular compound having a cationic property and the other layer comprised of an electrolytic high molecular compound having an anionic property. And according to the description of this document, it is understood that due to the presence of a solvent of an aqueous ink and molecules of a dye in a strong interaction (or an attraction) between an anion and cation which are locally distributed in the two-layered ink-receiving layer, not only molecules of the solvent but also the dye molecules are strongly prevented from being mobilized to result in providing an improvement in the apparent ink-fixing property and waterfastness. However, in practice, the use of the two-layered ink-receiving layer entails a drawback in that the aqueous ink is difficult to be dried quickly and therefore, there cannot be attained desirable fixing for the aqueous ink.
Japanese Unexamined Patent Publication No. 242578/1987 discloses a composition comprising a mixture of a cationic high-molecular compound and a high-molecular compound crosslinkable with the irradiation of ultraviolet rays which is suitable for the formation of an ink-receiving layer. According to the description of this document, it is understood that an ink-receiving layer formed of said composition is capable of trapping a dye of an aqueous ink by virtue of the cationic functional group of the cationic high-molecular compound, and when the ink-receiving layer is crosslinked with the irradiation of ultraviolet rays, it develops a structure with waterfastness. However, as for the ink-receiving layer, there are problems in that the two high-molecular compounds by which the ink-receiving layer is composed are likely to form a polyion complex between them, resulting in a marked reduction in the solubility of the composition to solvents used upon the formation of the ink-receiving layer by way of a coating process. In addition, the ink-receiving layer formed is of a remarkably inferior preservation stability even at room temperature and because of this, the ink-receiving property of the ink-receiving layer is gradually deteriorated during storage.
Japanese Unexamined Patent Publication No. 229685/1989 discloses an ink-receiving layer formed by subjecting a composition composed of a water soluble high-molecular compound and a hydrophilic oligomer having a terminal acryloyl group to crosslinking treatment. However, in practice, there is a considerable difference between the hydrophilic property possessed by the ink-receiving layer and the hydrophilic property required for an ink-receiving layer used in the ink jet printing using a water-based ink. Particularly, the ink-receiving layer described in this document does not easily satisfy the requirements relating to the ink receiving quantity and ink penetration speed in the printing by means of a color ink jet printing apparatus which has been widely using in recent years.
Japanese Unexamined Patent Publication No. 286886/1989 discloses curing materials comprising monofunctional or multifunctional monomers or oligomers which are suitable for the formation of an ink-receiving layer. This document also discloses materials capable of providing a cationic group required for the fixing of a dye. However the materials capable of providing a cationic group described in this document are monofunctional monomers and the multifunctional materials described in this document have no cationic group and therefore, they cannot form an ink-receiving layer having a desirable ink absorption rate and a desirable waterfastness at a curing rate practically employed upon the layer formation.
As apparent from the above description, in the prior art, there has not been proposed a crosslinkable composition which enables formation of an ink-receiving layer exhibiting a desirable absorptivity and absorption rate for water-based ink while exhibiting a fixing property for a coloring material of said water-based ink which are well compatible with the performance of the color ink jet printing apparatus which has been widely using in recent years.